staging: brcm80211: fix compiler warning introduced

Patch "[0f06b6a] remove WLC_WATCHDOG_TBTT macro" resulted
in compiler warning because static function wlc_watchdog_backup_bi()
is no longer used. This has been fixed in this patch.
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/brcm80211/brcmsmac/wlc_main.c

@@ -732,22 +732,6 @@ void wlc_set_chanspec(struct wlc_info *wlc, chanspec_t chanspec)
 	wlc_ucode_mac_upd(wlc);
 }
 
-static u32 wlc_watchdog_backup_bi(struct wlc_info *wlc)
-{
-	u32 bi;
-	bi = 2 * wlc->cfg->current_bss->dtim_period *
-	    wlc->cfg->current_bss->beacon_period;
-	if (wlc->bcn_li_dtim)
-		bi *= wlc->bcn_li_dtim;
-	else if (wlc->bcn_li_bcn)
-		/* recalculate bi based on bcn_li_bcn */
-		bi = 2 * wlc->bcn_li_bcn * wlc->cfg->current_bss->beacon_period;
-
-	if (bi < 2 * TIMER_INTERVAL_WATCHDOG)
-		bi = 2 * TIMER_INTERVAL_WATCHDOG;
-	return bi;
-}
-
 ratespec_t wlc_lowest_basic_rspec(struct wlc_info *wlc, wlc_rateset_t *rs)
 {
 	ratespec_t lowest_basic_rspec;